bomb dropped on hiroshima in 1945. no wonder nasa is keeping a closing watch for anything like it headed our way. at this moment, that near miss asteroid is now on its way out of the earth moon system. at 4 a.m. tomorrow, it will head outside the orbit of the moon. you can't see it without a powerful telescope. the magnitude is just about 7.4 well beyond naked iviesibility. but they will have telescopes at nasa you can watch it online. in the meantime, elizabeth, i have to tell you, what an extraordinary coincidence. we are sitting here waiting for this big near miss asteroid and then the real thing actually smashes into russia and it doesn't only smash into russia. it smashes as the biggest fall in 100 years and that last one in tunguska in 1908 was only 3,000 miles from this one. that's the longest astronomical hole in one you can possibly imagine. >> the video was incredible. >> reporter: incredible. >> i want to ask you, like, how often does this sort of thing happen asteroids and meteorites? how often do they come this close to earth?